The reduction of NOx from Diesel Engines or Lean-burn Gasoline Engines is a major issue in automotive catalysis. Over the last several years, many solutions to remove NOx under lean operating conditions have been considered. Attention is now focused on two main technologies: (i) Selective Catalytic Reduction using ammonia as reductant (urea SCR) and (ii) NOx-Storage Catalyst (NSC).
This paper deals with materials for NOx storage catalysts. Even if the fresh NSC shows high efficiency, its durability is low due to a fast deactivation of the active sites [1,3]. This problem relates to a drastic sintering of the materials after ageing, especially during the regeneration and the desulfation [3, 4 and 5]. Moreover, the current materials are sensitive to SOx poisoning [1,3, 4].
In this paper, modified Ba-alumina oxides used as NOx-Storage materials have been investigated. These oxides contain high Ba loading (such as 20 wt% Ba) and are thermally stable. They present high surface area (more than 100 m2/g) and available Ba sites for the NOx-Storage process after ageing at 900°C.
The corresponding aged Pt model catalysts show high NOx-Storage capacity from 200°C to 450°C, even after hydrothermal ageing at 700°C and sulfation treatments. The low temperature NSC efficiency can further be increased by adding a third compound, such as ceria, without decreasing the high temperature NSC performances.